1. Field of the Invention
The present invention is directed to a method and a device for activating at least one triggering element for a passenger protection means.
2. Description of the Related Art
Passenger protection systems known from the related art do not have a firing mode for activation circuits having low-energy actuators (LEA). These magnetic actuators are used, for example, for triggering of roll bars, in head protection systems for convertibles and/or for triggering of devices for raising engine hoods in pedestrian protection systems.
Use of known firing modes for pyrotechnic airbag actuators according to the valid safety requirements using firing currents of 1.2 A and a pulse duration of 2 ms or 1.75 A and having a pulse duration of 0.5 ms does not meet the safety requirements for low-energy actuators (LEA), which require a current in the range of 1.5 A to 2.2 A having a pulse duration in the range of 1.0 ms to 1.5 ms. Furthermore, a total activation time period of 3 ms is necessary to also enable the gradual current rise of the inductive low-energy actuators (LEA) even at a low energy reserve voltage or battery voltage. Approaches known in the past have used discrete high-side output stages, for example, for triggering such circuits having low-energy actuators (LEA). Alternatively, special approaches having reduced requirements due to known pyrotechnic firing modes are satisfied by integrated high-side output stages. At a current of 1.5 to 2.2 A, simple implementation of the longer activation time period (3 ms) significantly increases the size of an integrated high-side output stage designed for a known pyrotechnic firing circuit.
Published German Patent Application document DE 10 2009 027 918 A1, for example, describes a system and a method for activating at least one triggering element for a passenger protection means. The system described there includes a high-side circuit, which establishes a first connection from an energy source to the at least one triggering element and a low-side circuit, which establishes a second connection from the at least one triggering element to ground. In addition, a regulation which regulates a tripping current for the at least one triggering element is provided, this regulation being associated with the high-side circuit and/or the low-side circuit. Furthermore, the high-side circuit and the low-side circuit each have two output stages, which are connected in parallel for regulation of the tripping current, per triggering element, at least one of the at least two output stages having a current regulation and one or multiple transistors connected in parallel. Scaling is possible by the parallelization of the output stages, i.e., higher and longer tripping current pulses are implemented with two or multiple output stages connected in parallel. The tripping current pulses result in firing of a firing device or in magnetic actuation of a passenger protection means.